Bottom Line:
However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC.At the same time, the present theoretical "resolution limit" to measure the square root of the density-viscosity product [Formula: see text] of a liquid medium or best resolution achievable with a QCM oscillator is determined.The QCM resolution limit for [Formula: see text] measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency.

ABSTRACTIn battery applications, particularly in automobiles, submarines and remote communications, the state of charge (SoC) is needed in order to manage batteries efficiently. The most widely used physical parameter for this is electrolyte density. However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC. This paper presents a Quartz Crystal Microbalance (QCM) sensor for electrolyte density-viscosity product measurements in lead acid batteries. The sensor is calibrated in H(2)SO(4) solutions in the battery electrolyte range to obtain sensitivity, noise and resolution. Also, real-time tests of charge and discharge are conducted placing the quartz crystal inside the battery. At the same time, the present theoretical "resolution limit" to measure the square root of the density-viscosity product [Formula: see text] of a liquid medium or best resolution achievable with a QCM oscillator is determined. Findings show that the resolution limit only depends on the characteristics of the liquid to be studied and not on frequency. The QCM resolution limit for [Formula: see text] measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency.

f11-sensors-12-10604: Oscillation frequency over four days after temperature compensation and Allan deviation.

Mentions:
Figure 10 shows the oscillation frequency of the sensor with the quartz resonator placed inside a fully charged battery (40% sulphuric acid) and the temperature of the electrolyte (battery at room temperature). Figure 11 shows the frequency values obtained after temperature compensation using Equations (14)–(17) and the Allan deviation for an averaging time from 1 to 30 s. The worst Allan value is 1.6 × 10−7 and therefore the resolution value is . If we compare this “in-situ” noise values with values obtained in calibration with sulfuric solutions (Table 1), it can be concluded that frequency noise increases slightly when the resonator is placed inside the battery cell, perhaps due to temperature compensation. However, with this resolution changes can still be detected in the SoC of about 0.2% with a time interval of 2 s.

f11-sensors-12-10604: Oscillation frequency over four days after temperature compensation and Allan deviation.

Mentions:
Figure 10 shows the oscillation frequency of the sensor with the quartz resonator placed inside a fully charged battery (40% sulphuric acid) and the temperature of the electrolyte (battery at room temperature). Figure 11 shows the frequency values obtained after temperature compensation using Equations (14)–(17) and the Allan deviation for an averaging time from 1 to 30 s. The worst Allan value is 1.6 × 10−7 and therefore the resolution value is . If we compare this “in-situ” noise values with values obtained in calibration with sulfuric solutions (Table 1), it can be concluded that frequency noise increases slightly when the resonator is placed inside the battery cell, perhaps due to temperature compensation. However, with this resolution changes can still be detected in the SoC of about 0.2% with a time interval of 2 s.

Bottom Line:
However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC.At the same time, the present theoretical "resolution limit" to measure the square root of the density-viscosity product [Formula: see text] of a liquid medium or best resolution achievable with a QCM oscillator is determined.The QCM resolution limit for [Formula: see text] measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency.

ABSTRACTIn battery applications, particularly in automobiles, submarines and remote communications, the state of charge (SoC) is needed in order to manage batteries efficiently. The most widely used physical parameter for this is electrolyte density. However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC. This paper presents a Quartz Crystal Microbalance (QCM) sensor for electrolyte density-viscosity product measurements in lead acid batteries. The sensor is calibrated in H(2)SO(4) solutions in the battery electrolyte range to obtain sensitivity, noise and resolution. Also, real-time tests of charge and discharge are conducted placing the quartz crystal inside the battery. At the same time, the present theoretical "resolution limit" to measure the square root of the density-viscosity product [Formula: see text] of a liquid medium or best resolution achievable with a QCM oscillator is determined. Findings show that the resolution limit only depends on the characteristics of the liquid to be studied and not on frequency. The QCM resolution limit for [Formula: see text] measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency.